package com.tanhua.server.interceptor;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.tanhua.common.utils.Cache;
import org.apache.commons.codec.digest.DigestUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
public class RedisCacheInterceptor implements HandlerInterceptor {
    @Value("${tanhua.cache.enable}")
    private Boolean enable;
    @Autowired
    private RedisTemplate<String,String> redisTemplate;
    private static final ObjectMapper MAPPER=new ObjectMapper();
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //缓存全局开关的校验
        if(!enable){
            return true;
        }
        //校验handler是否是HttpMethod
        if (!(handler instanceof HandlerMethod)){
            return true;
        }
        //判断是否为Get请求
        if(!(((HandlerMethod) handler).hasMethodAnnotation(GetMapping.class))){
            return true;
        }
        //判断是否添加了Cache注解
        if(!(((HandlerMethod) handler).hasMethodAnnotation(Cache.class))){
            return true;
        }
        //缓存命中
        String redisKey= createRedisKey(request);
        String cacheData = this.redisTemplate.opsForValue().get(redisKey);
        if(StringUtils.isEmpty(cacheData)){
            //缓存未命中
            return true;
        }
        // 将data数据进行响应
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/json; charset=utf-8");
        response.getWriter().write(cacheData);
        return false;
    }
    //生成redis中的key，规则：SERVER_CACHE_DATA_MD5（url+param+token）
    public static String createRedisKey(HttpServletRequest request) throws Exception {
        String url=request.getRequestURI();
        String param = MAPPER.writeValueAsString(request.getParameterMap());
        String token= request.getHeader("Authorization");
        String data= url+"_"+param+"_"+token;
        return "SERVER_CACHE_DATA_"+DigestUtils.md5Hex(data);
    }
}
